Combinations of lipo-chitooligosaccharides and methods for use in enhancing plant growth

ABSTRACT

Disclosed are methods of enhancing plant growth, comprising treating plant seed or the plant that germinates from the seed with an effective amount of at least two lipo-chitooligosaccharides, wherein upon harvesting the plant exhibits at least one of increased plant yield measured in terms of bushels/acre, increased root number, increased root length, increased root mass, increased root volume and increased leaf area, compared to untreated plants or plants harvested from untreated seed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority or the benefit under 35 U.S.C. 119 ofU.S. provisional application No. 61/538,325 filed Sep. 23, 2011, thecontents of which are fully incorporated herein by reference.

BACKGROUND OF THE INVENTION

The symbiosis between the gram-negative soil bacteria, Rhizobiaceae andBradyrhizobiaceae, and legumes such as soybean, is well documented. Thebiochemical basis for these relationships includes an exchange ofmolecular signaling, wherein the plant-to-bacteria signal compoundsinclude flavones, isoflavones and flavanones, and the bacteria-to-plantsignal compounds, which include the end products of the expression ofthe bradyrhizobial and rhizobial nod genes, known aslipo-chitooligosaccharides (LCOs). The symbiosis between these bacteriaand the legumes enables the legume to fix atmospheric nitrogen for plantgrowth, thus obviating a need for nitrogen fertilizers. Since nitrogenfertilizers can significantly increase the cost of crops and areassociated with a number of polluting effects, the agricultural industrycontinues its efforts to exploit this biological relationship anddevelop new agents and methods for improving plant yield withoutincreasing the use of nitrogen-based fertilizers.

U.S. Pat. No. 6,979,664 teaches a method for enhancing seed germinationor seedling emergence of a plant crop, comprising the steps of providinga composition that comprises an effective amount of at least onelipo-chitooligosaccharide and an agriculturally suitable carrier andapplying the composition in the immediate vicinity of a seed or seedlingin an effective amount for enhancing seed germination of seedlingemergence in comparison to an untreated seed or seedling.

Further development on this concept is taught in WO 2005/062899,directed to combinations of at least one plant inducer, namely an LCO,in combination with a fungicide, insecticide, or combination thereof, toenhance a plant characteristic such as plant stand, growth, vigor and/oryield. The compositions and methods are taught to be applicable to bothlegumes and non-legumes, and may be used to treat a seed (just prior toplanting), seedling, root or plant.

Similarly, WO 2008/085958 teaches compositions for enhancing plantgrowth and crop yield in both legumes and non-legumes, and which containLCOs in combination with another active agent such as a chitin orchitosan, a flavonoid compound, or an herbicide, and which can beapplied to seeds and/or plants concomitantly or sequentially. As in thecase of the '899 Publication, the '958 Publication teaches treatment ofseeds just prior to planting.

More recently, Halford, “Smoke Signals,” in Chem. Eng. News (Apr. 12,2010), at pages 37-38, reports that karrikins or butenolides which arecontained in smoke act as growth stimulants and spur seed germinationafter a forest fire, and can invigorate seeds such as corn, tomatoes,lettuce and onions that had been stored. These molecules are the subjectof U.S. Pat. No. 7,576,213.

There is, however, still a need for systems for improving or enhancingplant growth.

BRIEF SUMMARY OF THE INVENTION

A first aspect of the present invention is directed to a method ofenhancing plant growth, comprising a) treating (e.g., applying to) plantseed or a plant that germinates from the seed, with an effective amountof at least two lipo-chitooligosaccharides (LCO's), wherein uponharvesting the plant exhibits at least one of increased plant yieldmeasured in terms of bushels/acre, increased root number, increased rootlength, increased root mass, increased root volume and increased leafarea, compared to untreated plants or plants harvested from untreatedseed.

As is clear in context, the two LCO's are different from each other. Insome embodiments, treatment of the seed includes direct application ofthe at least two LCO's onto the seed, which may then be planted orstored for a period of time prior to planting. Treatment of the seed mayalso include indirect treatment such as by introducing the at least twoLCO's into the soil (known in the art as in-furrow application). In yetother embodiments, the at least two LCO's may be applied to the plantthat germinates from the seed, e.g., via foliar spray. The methods mayfurther include use of other agronomically beneficial agents, such asmicronutrients, plant signal molecules (such aslipo-chitooligosaccharides, chitinous compounds (e.g., COs), flavonoids,jasmonic acid, linoleic acid and linolenic acid and their derivatives,and karrikins), herbicides, fungicides and insecticides,phosphate-solubilizing microorganisms, diazotrophs (Rhizobialinoculants), and/or mycorrhizal fungi.

The methods of the present invention are applicable to legumes andnon-legumes alike. In some embodiments, the leguminous seed is soybeanseed. In some other embodiments, the seed that is treated isnon-leguminous seed such as a field crop seed, e.g., a cereal such ascorn, or a vegetable crop seed such as potato.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 2a show the chemical structures of twolipo-chitooligosaccharides compounds useful in the practice of thepresent invention.

FIGS. 1b and 2b show the chemical structures of the correspondingchitooligosaccharide compounds (CO's) that correspond to the LCO's inFIGS. 1a and 2a , and which are also useful in the practice of thepresent invention.

FIGS. 3a and 4a show the chemical structures of other LCO's (Mycfactors) useful in the practice of the present invention.

FIGS. 3b and 4b show the chemical structures of the corresponding MycCO's, also useful in the practice of the present invention.

FIG. 5 shows the chemical structure of a lipo-chitooligosaccharideuseful in the practice of the present invention.

FIG. 6 is a bar graph that illustrates the effect of inventivecombinations of LCO's treated on seeds of Macroptilium atropurpureum,compared to a control, expressed in terms of seedling length (root plusshoot in mm).

FIGS. 7 and 8 are bar graphs that illustrate the effect of an inventivecombination of LCO's, compared to a single LCO and a control, treated onMacroptilium atropurpureum plants, expressed in terms of leaf greenness.

FIG. 9 is a bar graph that illustrates the effect of an inventivecombination of LCO's, compared to a single LCO and a control, treated onMacroptilium atropurpureum plants, expressed in terms of number of totalflowers per treatment.

FIG. 10 is a bar graph that illustrates the effect of an inventivecombination of LCO's, compared to a single LCO and a control, treated onMacroptilium atropurpureum plants, expressed in terms of total number offruits per treatment.

FIG. 11 is a bar graph that illustrates the effect of an inventivecombination of LCO's, compared to a single LCO and a control, treated onMacroptilium atropurpureum plants, expressed in terms of average fruitnumber per plant.

FIG. 12 is a bar graph that illustrates the effect of an inventivecombination of LCO's, compared to a single LCO and a control, treated onMacroptilium atropurpureum plants, expressed in terms of total number ofaverage yield (in grams) per plant.

FIG. 13 is a bar graph that illustrates the effect of various inventivecombinations of LCO's, compared to single LCO's and a control (water),treated on tomato seeds, expressed in terms of average root length.

DETAILED DESCRIPTION

Lipo-chitooligosaccharide compounds (LCO's), also known in the art assymbiotic Nod signals or Nod factors, consist of an oligosaccharidebackbone of β-I,4-linked N-acetyl-D-glucosamine (“GlcNAc”) residues withan N-linked fatty acyl chain condensed at the non-reducing end. LCO'sdiffer in the number of GlcNAc residues in the backbone, in the lengthand degree of saturation of the fatty acyl chain, and in thesubstitutions of reducing and non-reducing sugar residues. See, e.g.,Denarie, et al., Ann. Rev. Biochem. 65:503-35 (1996), Hamel, et al.,Planta 232:787-806 (2010)(e.g., FIG. 1 therein which shows structures ofchitin, chitosan, CO's and corresponding Nod factors (LCO's)); Prome, etal., Pure & Appl. Chem. 70(1):55-60 (1998). An example of an LCO ispresented below as formula I

in which:

G is a hexosamine which can be substituted, for example, by an acetylgroup on the nitrogen, a sulfate group, an acetyl group and/or an ethergroup on an oxygen,

R₁, R₂, R₃, R₅, R₆ and R₇, which may be identical or different,represent H, CH₃ CO—, C_(X) H_(y) CO— where x is an integer between 0and 17, and y is an integer between 1 and 35, or any other acyl groupsuch as for example a carbamoyl,

R₄ represents a mono-, di- or triunsaturated aliphatic chain containingat least 12 carbon atoms, and n is an integer between 1 and 4.

LCOs may be obtained (isolated and/or purified) from bacteria such asRhizobia, e.g., Rhizobium sp., Bradyrhizobium sp., Sinorhizobium sp. andAzorhizobium sp. LCO structures are characteristic for each suchbacterial species, and each strain may produce multiple LCO's withdifferent structures. For example, specific LCOs from S. meliloti havealso been described in U.S. Pat. No. 5,549,718 as having the formula II:

in which R represents H or CH₃CO— and n is equal to 2 or 3.

Even more specific LCOs include NodRM, NodRM-1, NodRM-3. When acetylated(the R═CH₃ CO—), they become AcNodRM-1, and AcNodRM-3, respectively(U.S. Pat. No. 5,545,718).

LCOs from Bradyrhizobium japonicum are described in U.S. Pat. Nos.5,175,149 and 5,321,011. Broadly, they are pentasaccharide phytohormonescomprising methylfucose. A number of these B. japonicum-derived LCOs aredescribed: BjNod-V (C_(18:1)); BjNod-V (A_(C), C_(18:1)), BjNod-V(C_(16:1)); and BjNod-V (A_(C), C_(16:0)), with “V” indicating thepresence of five N-acetylglucosamines; “Ac” an acetylation; the numberfollowing the “C” indicating the number of carbons in the fatty acidside chain; and the number following the “:” the number of double bonds.

LCO's used in embodiments of the invention may be obtained (i.e.,isolated and/or purified) from bacterial strains that produce LCO's,such as strains of Azorhizobium, Bradyrhizobium (including B.japonicum), Mesorhizobium, Rhizobium (including R. leguminosarum),Sinorhizobium (including S. meliloti), and bacterial strains geneticallyengineered to produce LCO's. Combinations of two or more LCO's obtainedfrom these rhizobial and bradyrhizobial microorganisms are includedwithin the scope of the present invention.

LCO's are the primary determinants of host specificity in legumesymbiosis (Diaz, et al., Mol. Plant-Microbe Interactions 13:268-276(2000)). Thus, within the legume family, specific genera and species ofrhizobia develop a symbiotic nitrogen-fixing relationship with aspecific legume host. These plant-host/bacteria combinations aredescribed in Hungria, et al., Soil Biol. Biochem. 29:819-830 (1997),Examples of these bacteria/legume symbiotic partnerships include S.meliloti/alfalfa and sweet clover; R. leguminosarum biovar viciae/peasand lentils; R. leguminosarum biovar phaseoli/beans; Bradyrhizobiumjaponicum/soybeans; and R. leguminosarum biovar trifolii/red clover.Hungria also lists the effective flavonoid Nod gene inducers of therhizobial species, and the specific LCO structures that are produced bythe different rhizobial species. However, LCO specificity is onlyrequired to establish nodulation in legumes. In the practice of thepresent invention, use of a given LCO is not limited to treatment ofseed of its symbiotic legume partner, in order to achieve increasedplant yield measured in terms of bushels/acre, increased root number,increased root length, increased root mass, increased root volume andincreased leaf area, compared to plants harvested from untreated seed,or compared to plants harvested from seed treated with the signalmolecule just prior to or within a week or less of planting.

Thus, by way of further examples, LCO's and non-naturally occurringderivatives thereof that may be useful in the practice of the presentinvention are represented by the following formula:

wherein R₁ represents C14:0, 3OH—C14:0, iso-C15:0, C16:0, 3-OH—C16:0,iso-C15:0, C16:1, C16:2, C16:3, iso-C17:0, iso-C17:1, C18:0, 3OH—C18:0,C18:0/3-OH, C18:1, OH—C18:1, C18:2, C18:3, C18:4, C19:1 carbamoyl,C20:0, C20:1, 3-OH—C20:1, C20:1/3-OH, C20:2, C20:3, C22:1, andC18-26(ω-1)-OH (which according to D'Haeze, et al., Glycobiology12:79R-105R (2002), includes C18, C20, C22, C24 and C₂₋₆ hydroxylatedspecies and C16:1Δ9, C16:2 (Δ2,9) and C16:3 (Δ2,4,9)); R₂ representshydrogen or methyl; R₃ represents hydrogen, acetyl or carbamoyl; R₄represents hydrogen, acetyl or carbamoyl; R₅ represents hydrogen, acetylor carbamoyl; R₆ represents hydrogen, arabinosyl, fucosyl, acetyl,sulfate ester, 3-O—S-2-0-MeFuc, 2-0-MeFuc, and 4-0-AcFuc; R₇ representshydrogen, mannosyl or glycerol; R₈ represents hydrogen, methyl, or—CH₂OH; R₉ represents hydrogen, arabinosyl, or fucosyl; R₁₀ representshydrogen, acetyl or fucosyl; and n represents 0, 1, 2 or 3. Thestructures of the naturally occurring Rhizobial LCO's embraced by thisstructure are described in D'Haeze, et al., supra.

By way of even further additional examples, an LCO obtained from B.japonicum, illustrated in FIG. 1a , may be used to treat leguminous seedother than soybean and non-leguminous seed such as corn. As anotherexample, the LCO obtainable from Rhizobium leguminosarum biovar viciaeillustrated in FIG. 2a (designated LCO-V (C18:1), SP104) can be used totreat leguminous seed other than pea and non-legumes too. Thus, in someembodiments, the combination of the two LCO's illustrated in FIGS. 1aand 2a are used in the methods of the present invention.

Also encompassed by the present invention is use of LCO's obtained(i.e., isolated and/or purified) from a mycorrhizal fungi, such as fungiof the group Glomerocycota, e.g., Glomus intraradicus. The structures ofrepresentative LCOs obtained from these fungi are described in WO2010/049751 and WO 2010/049751 (the LCOs described therein also referredto as “Myc factors”). Representative mycorrhizal fungi-derived LCO's andnon-naturally occurring derivatives thereof are represented by thefollowing structure:

wherein n=1 or 2; R₁ represents C16, C16:0, C16:1, C16:2, C18:0,C18:1Δ9Z or C18:1Δ11Z; and R₂ represents hydrogen or SO₃H. In someembodiments, the LCO's are produced by the mycorrhizal fungi which areillustrated in FIGS. 3a and 4a . In some embodiments, these LCO's areused in the methods of the present invention.

In some other embodiments, one of the two LCO's used in the methods ofthe present invention is obtained from S. meliloti, and is illustratedin FIG. 5. Thus, in some embodiments of the present invention, the LCO'sinclude at least two of the LCO's illustrated in FIGS. 1a, 2a, 3a, 4aand 5. Broadly, the present invention includes use of any two or moreLCO's, including naturally occurring (e.g., rhizobial, bradyrhizobialand fungal), recombinant, synthetic and non-naturally occurringderivatives thereof. In some embodiments, both of the at least two LCO'sare recombinant.

Further encompassed by the present invention is use of synthetic LCOcompounds, such as those described in WO 2005/063784, and recombinantLCO's produced through genetic engineering. The basic, naturallyoccurring LCO structure may contain modifications or substitutions foundin naturally occurring LCO's, such as those described in Spaink, Crit.Rev. Plant Sci. 54:257-288 (2000) and D'Haeze, supra. Precursoroligosaccharide molecules (COs, which as described below, are alsouseful as plant signal molecules in the present invention) for theconstruction of LCOs may also be synthesized by genetically engineeredorganisms, e.g., as described in Samain, et al., Carbohydrate Res.302:35-42 (1997); Cottaz, et al., Meth. Eng. 7(4):311-7 (2005) andSamain, et al., J. Biotechnol. 72:33-47 (1999) (e.g., FIG. 1 thereinwhich shows structures of CO's that can be made recombinantly in E. coliharboring different combinations of genes nodBCHL). Thus, in someembodiments, combinations of at least two LCO's include combinations ofthe LCO's selected from the LCO's illustrated in FIGS. 1a, 2a, 3a, 4a ,and 5.

LCO's may be utilized in various forms of purity and may be used aloneor in the form of a culture of LCO-producing bacteria or fungi. Forexample, OPTIMIZE® (commercially available from Novozymes BioAg Limited)contains a culture of B. japonicum that produces an LCO (LCO-V(C18:1,MeFuc), MOR116) that is illustrated in FIG. 1a . Methods to providesubstantially pure LCO's include simply removing the microbial cellsfrom a mixture of LCOs and the microbe, or continuing to isolate andpurify the LCO molecules through LCO solvent phase separation followedby HPLC chromatography as described, for example, in U.S. Pat. No.5,549,718. Purification can be enhanced by repeated HPLC, and thepurified LCO molecules can be freeze-dried for long-term storage.Chitooligosaccharides (COs) as described above, may be used as startingmaterials for the production of synthetic LCOs. For the purposes of thepresent invention, recombinant LCO's suitable for use in the presentinvention are least 60% pure, e.g., at least 60% pure, at least 65%pure, at least 70% pure, at least 75% pure, at least 80% pure, at least85% pure, at least 90% pure, at least 91% pure, at least 92% pure, atleast 93% pure, at least 94% pure, at least 95% pure, at least 96% pure,at least 97% pure, at least 98% pure, at least 99% pure, up to 100%pure.

Seeds may be treated with the at least two LCO's in several ways such asspraying or dripping. Spray and drip treatment may be conducted byformulating an effective amount of the at least two LCO's in anagriculturally acceptable carrier, typically aqueous in nature, andspraying or dripping the composition onto seed via a continuous treatingsystem (which is calibrated to apply treatment at a predefined rate inproportion to the continuous flow of seed), such as a drum-type oftreater. These methods advantageously employ relatively small volumes ofcarrier so as to allow for relatively fast drying of the treated seed.In this fashion, large volumes of seed can be efficiently treated. Batchsystems, in which a predetermined batch size of seed and signal moleculecompositions are delivered into a mixer, may also be employed. Systemsand apparatus for performing these processes are commercially availablefrom numerous suppliers, e.g., Bayer CropScience (Gustafson).

In another embodiment, the treatment entails coating seeds with the atleast two LCO's. One such process involves coating the inside wall of around container with the composition, adding seeds, then rotating thecontainer to cause the seeds to contact the wall and the composition, aprocess known in the art as “container coating”. Seeds can be coated bycombinations of coating methods. Soaking typically entails use of anaqueous solution containing the plant growth enhancing agent. Forexample, seeds can be soaked for about 1 minute to about 24 hours (e.g.,for at least 1 min, 5 min, 10 min, 20 min, 40 min, 80 min, 3 hr, 6 hr,12 hr, 24 hr). Some types of seeds (e.g., soybean seeds) tend to besensitive to moisture. Thus, soaking such seeds for an extended periodof time may not be desirable, in which case the soaking is typicallycarried out for about 1 minute to about 20 minutes.

In those embodiments that entail storage of seed after application ofthe at least two LCO's, adherence of the LCO's to the seed over anyportion of time of the storage period is not critical. Without intendingto be bound by any particular theory of operation, Applicants believethat even to the extent that the treating may not cause the plant signalmolecule to remain in contact with the seed surface after treatment andduring any part of storage, the LCO's may achieve their intended effectby a phenomenon known as seed memory or seed perception. See,Macchiavelli, et al., J. Exp. Bot. 55(408):1635-40 (2004). Applicantsalso believe that following treatment the LCO's diffuse toward the youngdeveloping radicle and activates symbiotic and developmental genes whichresults in a change in the root architecture of the plant.Notwithstanding, to the extent desirable, the compositions containingthe LCO's may further contain a sticking or coating agent. For aestheticpurposes, the compositions may further contain a coating polymer and/ora colorant.

In some embodiments, the at least two LCO's are applied to seed(directly or indirectly) or to the plant via the same composition (thatis, they are formulated together). In other embodiments, they areformulated separately, wherein both LCO compositions are applied to seedor the plant, or in some embodiments, one of the LCO's is applied toseed and the other is applied to the plant.

The total amount of the at least two LCO's is effective to enhancegrowth such that upon harvesting the plant exhibits at least one ofincreased plant yield measured in terms of bushels/acre, increased rootnumber, increased root length, increased root mass, increased rootvolume and increased leaf area, compared to untreated plants or plantsharvested from untreated seed (with either active). The effective amountof the at least two LCO's used to treat the seed, expressed in units ofconcentration, generally ranges from about 10⁻⁵ to about 10⁻¹⁴ M (molarconcentration), and in some embodiments, from about 10⁻⁵ to about 10⁻¹¹M, and in some other embodiments from about 10⁻⁷ to about 10⁻⁵ M.Expressed in units of weight, the effective amount generally ranges fromabout 1 to about 400 μg/hundred weight (cwt) seed, and in someembodiments from about 2 to about 70 μg/cwt, and in some otherembodiments, from about 2.5 to about 3.0 μg/cwt seed.

For purposes of treatment of seed indirectly, i.e., in-furrow treatment,the effective amount of the at least two LCO's generally ranges from 1μg/acre to about 70 μg/acre, and in some embodiments, from about 50μg/acre to about 60 μg/acre. For purposes of application to the plants,the effective amount of the LCO's generally ranges from 1 μg/acre toabout 30 μg/acre, and in some embodiments, from about 11 μg/acre toabout 20 μg/acre.

Seed may be treated with the at least two LCO's just prior to or at thetime of planting. Treatment at the time of planting may include directapplication to the seed as described above, or in some otherembodiments, by introducing the actives into the soil, known in the artas in-furrow treatment. In those embodiments that entail treatment ofseed followed by storage, the seed may be then packaged, e.g., in 50-lbor 100-lb bags, or bulk bags or containers, in accordance with standardtechniques. The seed may be stored for at least 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 11, or 12 months, and even longer, e.g., 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36months, or even longer, under appropriate storage conditions which areknown in the art. Whereas soybean seed may have to be planted thefollowing season, corn seed can be stored for much longer periods oftime including upwards of 3 years.

Other Agronomically Beneficial Agents

The present invention may further include treatment of the seed or theplants that germinate from the seed with at least oneagriculturally/agronomically beneficial agent. As used herein and in theart, the term “agriculturally or agronomically beneficial” refers toagents that when applied to seeds or plants results in enhancement(which may be statistically significant) of plant characteristics suchas plant stand, growth (e.g., as defined in connection with LCO's), orvigor in comparison to non-treated seeds or plants. These agents may beformulated together with the at least two LCO's or applied to the seedor plant via a separate formulation. Representative examples of suchagents that may be useful in the practice of the present inventioninclude micronutrients (e.g., vitamins and trace minerals), plant signalmolecules (other than LCO's), herbicides, fungicides and insecticides,phosphate-solubilizing microorganisms, diazotrophs (Rhizobialinoculants), and/or mycorrhizal fungi.

Micronutrients

Representative vitamins that may be useful in the practice of thepresent invention include calcium pantothenate, folic acid, biotin, andvitamin C. Representative examples of trace minerals that may be usefulin the practice of the present invention include boron, chlorine,manganese, iron, zinc, copper, molybdenum, nickel, selenium and sodium.

The amount of the at least one micronutrient used to treat the seed,expressed in units of concentration, generally ranges from 10 ppm to 100ppm, and in some embodiments, from about 2 ppm to about 100 ppm.Expressed in units of weight, the effective amount generally ranges inone embodiment from about 180 μg to about 9 mg/hundred weight (cwt)seed, and in some embodiments from about 4 μg to about 200 μg/plant whenapplied on foliage. In other words, for purposes of treatment of seedthe effective amount of the at least one micronutrient generally rangesfrom 30 μg/acre to about 1.5 mg/acre, and in some embodiments, fromabout 120 mg/acre to about 6 g/acre when applied foliarly.

Plant Signal Molecules

The present invention may also include treatment of seed or plant with aplant signal molecule other than an LCO. For purposes of the presentinvention, the term “plant signal molecule”, which may be usedinterchangeably with “plant growth-enhancing agent” broadly refers toany agent, both naturally occurring in plants or microbes, and synthetic(and which may be non-naturally occurring) that directly or indirectlyactivates a plant biochemical pathway, resulting in increased plantgrowth, measureable at least in terms of at least one of increased yieldmeasured in terms of bushels/acre, increased root number, increased rootlength, increased root mass, increased root volume and increased leafarea, compared to untreated plants or plants harvested from untreatedseed. Representative examples of plant signal molecules that may beuseful in the practice of the present invention include chitinouscompounds, flavonoids, jasmonic acid, linoleic acid and linolenic acidand their derivatives (supra), and karrikins.

Chitooligosaccharides

COs are known in the art as β-1-4 linked N-acetyl glucosamine structuresidentified as chitin oligomers, also as N-acetylchitooligosaccharides.CO's have unique and different side chain decorations which make themdifferent from chitin molecules [(C₈H₁₃NO₅)_(n), CAS No. 1398-61-4], andchitosan molecules [(C₅H₁₁NO₄)_(n), CAS No. 9012-76-4]. The CO's of thepresent invention are also relatively water-soluble compared to chitinand chitosan, and in some embodiments, as described hereinbelow, arepentameric. Representative literature describing the structure andproduction of COs that may be suitable for use in the present inventionis as follows: Muller, et al., Plant Physiol. 124:733-9 (2000); Van derHolst, et al., Current Opinion in Structural Biology, 11:608-616(2001)(e.g., FIG. 1 therein); Robina, et al., Tetrahedron 58:521-530(2002); D'Haeze, et al., Glycobiol. 12(6):79R-105R (2002); Hamel, etal., Planta 232:787-806 (2010)(e.g., FIG. 1 which shows structures ofchitin, chitosan, CO's and corresponding Nod factors (LCO's)); Rouge, etal. Chapter 27, “The Molecular Immunology of Complex Carbohydrates” inAdvances in Experimental Medicine and Biology, Springer Science; Wan, etal., Plant Cell 21:1053-69 (2009); PCT/F100/00803 (Sep. 21, 2000); andDemont-Caulet, et al., Plant Physiol. 120(1):83-92 (1999).

CO's differ from LCO's in terms of structure mainly in that they lackthe pendant fatty acid chain. Rhizobia-derived CO's, and non-naturallyoccurring synthetic derivatives thereof, that may be useful in thepractice of the present invention may be represented by the followingformula:

wherein R₁ and R₂ each independently represents hydrogen or methyl; R₃represents hydrogen, acetyl or carbamoyl; R₄ represents hydrogen, acetylor carbamoyl; R₅ represents hydrogen, acetyl or carbamoyl; R₆ representshydrogen, arabinosyl, fucosyl, acetyl, sulfate ester, 3-0-S-2-0-MeFuc,2-0-MeFuc, and 4-0-AcFuc; R₇ represents hydrogen, mannosyl or glycerol;R₈ represents hydrogen, methyl, or —CH₂OH; R₉ represents hydrogen,arabinosyl, or fucosyl; R₁₀ represents hydrogen, acetyl or fucosyl; andn represents 0, 1, 2 or 3. The structures of corresponding RhizobialLCO's are described in D'Haeze, et al., supra.

Two CO's suitable for use in the present invention are illustrated inFIGS. 1b and 2b . They correspond to LCO's produced by Bradyrhizobiumjaponicum and R. leguminosarum biovar viciae respectively, whichinteract symbiotically with soybean and pea, respectively, but lack thefatty acid chains.

The structures of yet other CO's that may be suitable for use in thepractice of the present invention are easily derivable from LCOsobtained (i.e., isolated and/or purified) from a mycorrhizal fungi, suchas fungi of the group Glomerocycota, e.g., Glomus intraradices. See,e.g., WO 2010/049751 and Maillet, et al., Nature 469:58-63 (2011) (theLCOS described therein also referred to as “Myc factors”).Representative mycorrhizal fungi-derived CO's are represented by thefollowing structure:

wherein n=1 or 2; R₁ represents hydrogen or methyl; and R₂ representshydrogen or SO₃H. Two other CO's suitable for use in the presentinvention, one of which is sulfated, and the other being non-sulfated,are illustrated in FIGS. 3b and 4b respectively. They correspond toaforementioned two different LCO's produced by the mycorrhizal fungiGlomus intraradices, and which are illustrated in FIGS. 3a and 4 a.

The COs may be synthetic or recombinant. Methods for preparation ofsynthetic CO's are described, for example, in Robina, supra. Methods forproducing recombinant CO's e.g., using E. coli as a host, are known inthe art. See, e.g., Dumon, et al., ChemBioChem 7:359-65 (2006), Samain,et al., Carbohydrate Res. 302:35-42 (1997); Cottaz, et al., Meth. Eng.7(4):311-7 (2005) and Samain, et al., J. Biotechnol. 72:33-47(1999)(e.g., FIG. 1 therein which shows structures of CO's that can bemade recombinantly in E. coli harboring different combinations of genesnodBCHL). For the purposes of the present invention, the recombinantCO's are at least 60% pure, e.g., at least 60% pure, at least 65% pure,at least 70% pure, at least 75% pure, at least 80% pure, at least 85%pure, at least 90% pure, at least 91% pure, at least 92% pure, at least93% pure, at least 94% pure, at least 95% pure, at least 96% pure, atleast 97% pure, at least 98% pure, at least 99% pure, up to 100% pure.

Other chitinous compounds include chitins and chitosans, which are majorcomponents of the cell walls of fungi and the exoskeletons of insectsand crustaceans, are also composed of GlcNAc residues. Chitinouscompounds include chitin, (IUPAC:N-[5-[[3-acetylamino-4,5-dihydroxy-6-(hydroxymethyl)oxan-2yl]methoxymethyl]-2-[[5-acetylamino-4,6-dihydroxy-2-(hydroxymethyl)oxan-3-yl]methoxymethyl]-4-hydroxy-6-(hydroxymethyl)oxan-3-ys]ethanamide),and chitosan, (IUPAC:5-amino-6-[5-amino-6-[5-amino-4,6-dihydroxy-2(hydroxymethyl)oxan-3-yl]oxy-4-hydroxy-2-(hydroxymethyl)oxan-3-yl]oxy-2(hydroxymethyl)oxane-3,4-diol).These compounds may be obtained commercially, e.g., from Sigma-Aldrich,or prepared from insects, crustacean shells, or fungal cell walls.Methods for the preparation of chitin and chitosan are known in the art,and have been described, for example, in U.S. Pat. No. 4,536,207(preparation from crustacean shells), Pochanavanich, et al., Lett. Appl.Microbiol. 35:17-21 (2002) (preparation from fungal cell walls), andU.S. Pat. No. 5,965,545 (preparation from crab shells and hydrolysis ofcommercial chitosan). See, also, Jung, et al., Carbohydrate Polymers67:256-59 (2007); Khan, et al., Photosynthetica 40(4):621-4 (2002).Deacetylated chitins and chitosans may be obtained that range from lessthan 35% to greater than 90% deacetylation, and cover a broad spectrumof molecular weights, e.g., low molecular weight chitosan oligomers ofless than 15 kD and chitin oligomers of 0.5 to 2 kD; “practical grade”chitosan with a molecular weight of about 150 kD; and high molecularweight chitosan of up to 700 kD. Chitin and chitosan compositionsformulated for seed treatment are also commercially available.Commercial products include, for example, ELEXA® (Plant DefenseBoosters, Inc.) and BEYOND™ (Agrihouse, Inc.).

Flavonoids are phenolic compounds having the general structure of twoaromatic rings connected by a three-carbon bridge. Flavonoids areproduced by plants and have many functions, e.g., as beneficialsignaling molecules, and as protection against insects, animals, fungiand bacteria. Classes of flavonoids include chalcones, anthocyanidins,coumarins, flavones, flavanols, flavonols, flavanones, and isoflavones.See, Jain, et al., J. Plant Biochem. & Biotechnol. 11:1-10 (2002); Shaw,et al., Environmental Microbiol. 11:1867-80 (2006).

Representative flavonoids that may be useful in the practice of thepresent invention include genistein, daidzein, formononetin, naringenin,hesperetin, luteolin, and apigenin. Flavonoid compounds are commerciallyavailable, e.g., from Natland International Corp., Research TrianglePark, N.C.; MP Biomedicals, Irvine, Calif.; LC Laboratories, WoburnMass. Flavonoid compounds may be isolated from plants or seeds, e.g., asdescribed in U.S. Pat. Nos. 5,702,752; 5,990,291; and 6,146,668.Flavonoid compounds may also be produced by genetically engineeredorganisms, such as yeast, as described in Ralston, et al., PlantPhysiology 137:1375-88 (2005).

Jasmonic acid (JA, [1R-[1α,2β(Z)]]-3-oxo-2-(pentenyl)cyclopentaneaceticacid) and its derivatives (which include linoleic acid and linolenicacid (which are described above in connection with fatty acids and theirderivatives), may be used in the practice of the present invention.Jasmonic acid and its methyl ester, methyl jasmonate (MeJA),collectively known as jasmonates, are octadecanoid-based compounds thatoccur naturally in plants. Jasmonic acid is produced by the roots ofwheat seedlings, and by fungal microorganisms such as Botryodiplodiatheobromae and Gibbrella fujikuroi, yeast (Saccharomyces cerevisiae),and pathogenic and non-pathogenic strains of Escherichia coli. Linoleicacid and linolenic acid are produced in the course of the biosynthesisof jasmonic acid. Like linoleic acid and linolenic acid, jasmonates (andtheir derivatives) are reported to be inducers of nod gene expression orLCO production by rhizobacteria. See, e.g., Mabood, Fazli, Jasmonatesinduce the expression of nod genes in Bradyrhizobium japonicum, May 17,2001.

Useful derivatives of jasmonic acid, linoleic acid and linolenic acidthat may be useful in the practice of the present invention includeesters, amides, glycosides and salts. Representative esters arecompounds in which the carboxyl group of jasmonic acid, linoleic acidand linolenic acid has been replaced with a —COR group, where R is an—OR¹ group, in which R¹ is: an alkyl group, such as a C₁-C₈ unbranchedor branched alkyl group, e.g., a methyl, ethyl or propyl group; analkenyl group, such as a C₂-C₈ unbranched or branched alkenyl group; analkynyl group, such as a C₂-C₈ unbranched or branched alkynyl group; anaryl group having, for example, 6 to 10 carbon atoms; or a heteroarylgroup having, for example, 4 to 9 carbon atoms, wherein the heteroatomsin the heteroaryl group can be, for example, N, O, P, or S.Representative amides are compounds in which the carboxyl group ofjasmonic acid, linoleic acid and linolenic acid has been replaced with a—COR group, where R is an NR²R³ group, in which R² and R³ areindependently: hydrogen; an alkyl group, such as a C₁-C₈ unbranched orbranched alkyl group, e.g., a methyl, ethyl or propyl group; an alkenylgroup, such as a C₂-C₈ unbranched or branched alkenyl group; an alkynylgroup, such as a C₂-C₈ unbranched or branched alkynyl group; an arylgroup having, for example, 6 to 10 carbon atoms; or a heteroaryl grouphaving, for example, 4 to 9 carbon atoms, wherein the heteroatoms in theheteroaryl group can be, for example, N, O, P, or S. Esters may beprepared by known methods, such as acid-catalyzed nucleophilic addition,wherein the carboxylic acid is reacted with an alcohol in the presenceof a catalytic amount of a mineral acid. Amides may also be prepared byknown methods, such as by reacting the carboxylic acid with theappropriate amine in the presence of a coupling agent such asdicyclohexyl carbodiimide (DCC), under neutral conditions. Suitablesalts of jasmonic acid, linoleic acid and linolenic acid include e.g.,base addition salts. The bases that may be used as reagents to preparemetabolically acceptable base salts of these compounds include thosederived from cations such as alkali metal cations (e.g., potassium andsodium) and alkaline earth metal cations (e.g., calcium and magnesium).These salts may be readily prepared by mixing together a solution oflinoleic acid, linolenic acid, or jasmonic acid with a solution of thebase. The salt may be precipitated from solution and be collected byfiltration or may be recovered by other means such as by evaporation ofthe solvent.

Karrikins are vinylogous 4H-pyrones e.g., 2H-furo[2,3-c]pyran-2-onesincluding derivatives and analogues thereof. Examples of these compoundsare represented by the following structure:

wherein; Z is O, S or NR₅; R₁, R₂, R₃, and R₄ are each independently H,alkyl, alkenyl, alkynyl, phenyl, benzyl, hydroxy, hydroxyalkyl, alkoxy,phenyloxy, benzyloxy, CN, COR₆, COOR═, halogen, NR₆R₇, or NO₂; and R₅,R₆, and R₇ are each independently H, alkyl or alkenyl, or a biologicallyacceptable salt thereof. Examples of biologically acceptable salts ofthese compounds may include acid addition salts formed with biologicallyacceptable acids, examples of which include hydrochloride, hydrobromide,sulphate or bisulphate, phosphate or hydrogen phosphate, acetate,benzoate, succinate, fumarate, maleate, lactate, citrate, tartrate,gluconate; methanesulphonate, benzenesulphonate and p-toluenesulphonicacid. Additional biologically acceptable metal salts may include alkalimetal salts, with bases, examples of which include the sodium andpotassium salts. Examples of compounds embraced by the structure andwhich may be suitable for use in the present invention include thefollowing: 3-methyl-2H-furo[2,3-c]pyran-2-one (where R₁═CH₃, R₂, R₃,R₄═H), 2H-furo[2,3-c]pyran-2-one (where R₁, R₂, R₃, R₄═H),7-methyl-2H-furo[2,3-c]pyran-2-one (where R₁, R₂, R₄═H, R₃═CH₃),5-methyl-2H-furo[2,3-c]pyran-2-one (where R₁, R₂, R₃═H, R₄═CH₃),3,7-dimethyl-2H-furo[2,3-c]pyran-2-one (where R₁, R₃═CH₃, R₂, R₄═H),3,5-dimethyl-2H-furo[2,3-c]pyran-2-one (where R₁, R₄═CH₃, R₂, R₃═H),3,5,7-trimethyl-2H-furo[2,3-c]pyran-2-one (where R₁, R₃, R₄═CH₃, R₂═H),5-methoxymethyl-3-methyl-2H-furo[2,3-c]pyran-2-one (where R₁═CH₃, R₂,R₃═H, R₄═CH₂OCH₃), 4-bromo-3,7-dimethyl-2H-furo[2,3-c]pyran-2-one (whereR₁, R₃═CH₃, R₂=Br, R₄═H), 3-methylfuro[2,3-c]pyridin-2(3H)-one (whereZ═NH, R₁═CH₃, R₂, R₃, R₄═H), 3,6-dimethylfuro[2,3-c]pyridin-2(6H)-one(where Z═N—CH₃, R₁═CH₃, R₂, R₃, R₄═H). See, U.S. Pat. No. 7,576,213.These molecules are also known as karrikins. See, Halford, supra.

The amount of the at least one plant signal molecule used to treat theseed, expressed in units of concentration, generally ranges from about10⁻⁵ to about 10⁻¹⁴ M (molar concentration), and in some embodiments,from about 10⁻⁵ to about 10⁻¹¹M, and in some other embodiments fromabout 10⁻⁷ to about 10⁻⁸ M. Expressed in units of weight, the effectiveamount generally ranges from about 1 to about 400 μg/hundred weight(cwt) seed, and in some embodiments from about 2 to about 70 μg/cwt, andin some other embodiments, from about 2.5 to about 3.0 μg/cwt seed.

For purposes of treatment of seed indirectly, i.e., in-furrow treatment,the effective amount of the at least one plant signal molecule generallyranges from 1 μg/acre to about 70 μg/acre, and in some embodiments, fromabout 50 μg/acre to about 60 μg/acre. For purposes of application to theplants, the effective amount of the at least one plant signal moleculegenerally ranges from 1 μg/acre to about 30 μg/acre, and in someembodiments, from about 11 μg/acre to about 20 μg/acre.

Herbicides, Fungicides and Insecticides

Suitable herbicides include bentazon, acifluorfen, chlorimuron,lactofen, clomazone, fluazifop, glufosinate, glyphosate, sethoxydim,imazethapyr, imazamox, fomesafe, flumiclorac, imazaquin, and clethodim.Commercial products containing each of these compounds are readilyavailable. Herbicide concentration in the composition will generallycorrespond to the labeled use rate for a particular herbicide.

A “fungicide” as used herein and in the art, is an agent that kills orinhibits fungal growth. As used herein, a fungicide “exhibits activityagainst” a particular species of fungi if treatment with the fungicideresults in killing or growth inhibition of a fungal population (e.g., inthe soil) relative to an untreated population. Effective fungicides inaccordance with the invention will suitably exhibit activity against abroad range of pathogens, including but not limited to Phytophthora,Rhizoctonia, Fusarium, Pythium, Phomopsis or Selerotinia and Phakopsoraand combinations thereof.

Commercial fungicides may be suitable for use in the present invention.Suitable commercially available fungicides include PROTÉGÉ, RIVAL orALLEGIANCE FL or LS (Gustafson, Plano, Tex.), WARDEN RTA (Agrilance, St.Paul, Minn.), APRON XL, APRON MAXX RTA or RFC, MAXIM 4FS or XL(Syngenta, Wilmington, Del.), CAPTAN (Arvesta, Guelph, Ontario) andPROTREAT (Nitragin Argentina, Buenos Ares, Argentina). Activeingredients in these and other commercial fungicides include, but arenot limited to, fludioxonil, mefenoxam, azoxystrobin and metalaxyl.Commercial fungicides are most suitably used in accordance with themanufacturer's instructions at the recommended concentrations.

As used herein, an insecticide “exhibits activity against” a particularspecies of insect if treatment with the insecticide results in killingor inhibition of an insect population relative to an untreatedpopulation. Effective insecticides in accordance with the invention willsuitably exhibit activity against a broad range of insects including,but not limited to, wireworms, cutworms, grubs, corn rootworm, seed cornmaggots, flea beetles, chinch bugs, aphids, leaf beetles, and stinkbugs.

Commercial insecticides may be suitable for use in the presentinvention. Suitable commercially-available insecticides include CRUISER(Syngenta, Wilmington, Del.), GAUCHO and PONCHO (Gustafson, Plano,Tex.). Active ingredients in these and other commercial insecticidesinclude thiamethoxam, clothianidin, and imidacloprid. Commercialinsecticides are most suitably used in accordance with themanufacturer's instructions at the recommended concentrations.

Phosphate Solubilizing Microorganisms, Diazotrophs (Rhizobialinoculants), and/or Mycorrhizal Fungi.

The present invention may further include treatment of the seed with aphosphate solubilizing microorganism. As used herein, “phosphatesolubilizing microorganism” is a microorganism that is able to increasethe amount of phosphorous available for a plant. Phosphate solubilizingmicroorganisms include fungal and bacterial strains. In embodiment, thephosphate solubilizing microorganism is a spore forming microorganism.

Non-limiting examples of phosphate solubilizing microorganisms includespecies from a genus selected from the group consisting ofAcinetobacter, Arthrobacter, Arthrobotrys, Aspergillus, Azospirillum,Bacillus, Burkholderia, Candida Chryseomonas, Enterobacter,Eupenicillium, Exiguobacterium, Klebsiella, Kluyvera, Microbacterium,Mucor, Paecilomyces, Paenibacillus, Penicillium, Pseudomonas, Serratia,Stenotrophomonas, Streptomyces, Streptosporangium, Swaminathania,Thiobacillus, Torulospora, Vibrio, Xanthobacter, and Xanthomonas.

Non-limiting examples of phosphate solubilizing microorganisms areselected from the group consisting Acinetobacter calcoaceticus,Acinetobacter sp, Arthrobacter sp., Arthrobotrys oligospora, Aspergillusniger, Aspergillus sp., Azospirillum halopraeferans, Bacillusamyloliquefaciens, Bacillus atrophaeus, Bacillus circulans, Bacilluslicheniformis, Bacillus subtilis, Burkholderia cepacia, Burkholderiavietnamiensis, Candida krissii, Chryseomonas luteola, Enterobacteraerogenes, Enterobacter asburiae, Enterobacter sp., Enterobactertaylorae, Eupenicillium parvum, Exiguobacterium sp., Klebsiella sp.,Kluyvera cryocrescens, Microbacterium sp., Mucor ramosissimus,Paecilomyces hepialid, Paecilomyces marquandii, Paenibacillus macerans,Paenibacillus mucilaginosus, Pantoea aglomerans, Penicillium expansum,Pseudomonas corrugate, Pseudomonas fluorescens, Pseudomonas lutea,Pseudomonas poae, Pseudomonas putida, Pseudomonas stutzeri, Pseudomonastrivialis, Serratia marcescens, Stenotrophomonas maltophilia,Streptomyces sp., Streptosporangium sp., Swaminathania salitolerans,Thiobacillus ferrooxidans, Torulospora globosa, Vibrio proteolyticus,Xanthobacter agilis, and Xanthomonas campestris

In a particular embodiment, the phosphate solubilizing microorganism isa strain of the fungus Penicillium. Strains of the fungus Penicilliumthat may be useful in the practice of the present invention include P.bilaiae (formerly known as P. bilaii), P. albidum, P. aurantiogriseum,P. chrysogenum, P. citreonigrum, P. citrinum, P. digitatum, P.frequentas, P. fuscum, P. gaestrivorus, P. glabrum, P. griseofulvum, P.implicatum, P. janthinellum, P. lilacinum, P. minioluteum, P.montanense, P. nigricans, P. oxalicum, P. pinetorum, P. pinophilum, P.purpurogenum, P. radicans, P. radicum, P. raistrickii, P. rugulosum, P.simplicissimum, P. solitum, P. variabile, P. velutinum, P. viridicatum,P. glaucum, P. fussiporus, and P. expansum.

In one particular embodiment, the Penicillium species is P. bilaiae. Inanother particular embodiment the P. bilaiae strains are selected fromthe group consisting of ATCC 20851, NRRL 50169, ATCC 22348, ATCC 18309,NRRL 50162 (Wakelin, et al., 2004. Biol Fertil Soils 40:36-43). Inanother particular embodiment the Penicillium species is P.gaestrivorus, e.g., NRRL 50170 (see, Wakelin, supra.).

In some embodiments, more than one phosphate solubilizing microorganismis used, such as, at least two, at least three, at least four, at leastfive, at least 6, including any combination of the Acinetobacter,Arthrobacter, Arthrobotrys, Aspergillus, Azospirillum, Bacillus,Burkholderia, Candida Chryseomonas, Enterobacter, Eupenicillium,Exiguobacterium, Klebsiella, Kluyvera, Microbacterium, Mucor,Paecilomyces, Paenibacillus, Penicillium, Pseudomonas, Serratia,Stenotrophomonas, Streptomyces, Streptosporangium, Swaminathania,Thiobacillus, Torulospora, Vibrio, Xanthobacter, and Xanthomonas,including one species selected from the following group: Acinetobactercalcoaceticus, Acinetobacter sp, Arthrobacter sp., Arthrobotrysoligospora, Aspergillus niger, Aspergillus sp., Azospirillumhalopraeferans, Bacillus amyloliquefaciens, Bacillus atrophaeus,Bacillus circulans, Bacillus licheniformis, Bacillus subtilis,Burkholderia cepacia, Burkholderia vietnamiensis, Candida krissii,Chryseomonas luteola, Enterobacter aerogenes, Enterobacter asburiae,Enterobacter sp., Enterobacter taylorae, Eupenicillium parvum,Exiguobacterium sp., Klebsiella sp., Kluyvera cryocrescens,Microbacterium sp., Mucor ramosissimus, Paecilomyces hepialid,Paecilomyces marquandii, Paenibacillus macerans, Paenibacillusmucilaginosus, Pantoea aglomerans, Penicillium expansum, Pseudomonascorrugate, Pseudomonas fluorescens, Pseudomonas lutea, Pseudomonas poae,Pseudomonas putida, Pseudomonas stutzeri, Pseudomonas trivialis,Serratia marcescens, Stenotrophomonas maltophilia, Streptomyces sp.,Streptosporangium sp., Swaminathania salitolerans, Thiobacillusferrooxidans, Torulospora globosa, Vibrio proteolyticus, Xanthobacteragilis, and Xanthomonas campestris

In some embodiments, two different strains of the same species may alsobe combined, for example, at least two different strains of Penicilliumare used. The use of a combination of at least two different Penicilliumstrains has the following advantages. When applied to soil alreadycontaining insoluble (or sparingly soluble) phosphates, the use of thecombined fungal strains will result in an increase in the amount ofphosphorus available for plant uptake compared to the use of only onePenicillium strain. This in turn may result in an increase in phosphateuptake and/or an increase in yield of plants grown in the soil comparedto use of individual strains alone. The combination of strains alsoenables insoluble rock phosphates to be used as an effective fertilizerfor soils which have inadequate amounts of available phosphorus. Thus,in some embodiments, one strain of P. bilaiae and one strain of P.gaestrivorus are used. In other embodiments, the two strains are NRRL50169 and NRRL 50162. In further embodiments, the at least two strainsare NRRL 50169 and NRRL 50170. In yet further embodiments, the at leasttwo strains are NRRL 50162 and NRRL 50170.

The phosphate solubilizing microorganisms may be prepared using anysuitable method known to the person skilled in the art, such as, solidstate or liquid fermentation using a suitable carbon source. Thephosphate solubilizing microorganism is preferably prepared in the formof a stable spore.

In an embodiment, the phosphate solubilizing microorganism is aPenicillium fungus. The Penicillium fungus according to the inventioncan be grown using solid state or liquid fermentation and a suitablecarbon source. Penicillium isolates may be grown using any suitablemethod known to the person skilled in the art. For example, the fungusmay be cultured on a solid growth medium such as potato dextrose agar ormalt extract agar, or in flasks containing suitable liquid media such asCzapek-Dox medium or potato dextrose broth. These culture methods may beused in the preparation of an inoculum of Penicillium spp. for treating(e.g., coating) seeds and/or application to an agronomically acceptablecarrier to be applied to soil. The term “inoculum” as used in thisspecification is intended to mean any form of phosphate solubilizingmicroorganism, fungus cells, mycelium or spores, bacterial cells orbacterial spores, which is capable of propagating on or in the soil whenthe conditions of temperature, moisture, etc., are favorable for fungalgrowth.

Solid state production of Penicillium spores may be achieved byinoculating a solid medium such as a peat or vermiculite-basedsubstrate, or grains including, but not limited to, oats, wheat, barley,or rice. The sterilized medium (achieved through autoclaving orirradiation) is inoculated with a spore suspension (1×10²-1×10⁷ cfu/ml)of the appropriate Penicillium spp. and the moisture adjusted to 20 to50%, depending on the substrate. The material is incubated for 2 to 8weeks at room temperature. The spores may also be produced by liquidfermentation (Cunningham et al., 1990. Can J Bot. 68:2270-2274). Liquidproduction may be achieved by cultivating the fungus in any suitablemedia, such as potato dextrose broth or sucrose yeast extract media,under appropriate pH and temperature conditions that may be determinedin accordance with standard procedures in the art.

The resulting material may be used directly, or the spores may beharvested, concentrated by centrifugation, formulated, and then driedusing air drying, freeze drying, or fluid bed drying techniques(Friesen, et al., 2005, Appl. Microbiol. Biotechnol. 68:397-404) toproduce a wettable powder. The wettable powder is then suspended inwater, applied to the surface of seeds, and allowed to dry prior toplanting. The wettable powder may be used in conjunction with other seedtreatments, such as, but not limited to, chemical seed treatments,carriers (e.g., talc, clay, kaolin, silica gel, kaolinite) or polymers(e.g., methylcellulose, polyvinylpyrrolidone). Alternatively, a sporesuspension of the appropriate Penicillium spp. may be applied to asuitable soil-compatible carrier (e.g., peat-based powder or granule) toappropriate final moisture content. The material may be incubated atroom temperature, typically for about 1 day to about 8 weeks, prior touse.

Aside from the ingredients used to cultivate the phosphate solubilizingmicroorganism, including, e.g., ingredients referenced above in thecultivation of Penicillium, the phosphate solubilizing microorganism maybe formulated using other agronomically acceptable carriers. As usedherein in connection with “carrier”, the term “agronomically acceptable”refers to any material which can be used to deliver the actives to aseed, soil or plant, and preferably which carrier can be added (to theseed, soil or plant) without having an adverse effect on plant growth,soil structure, soil drainage or the like. Suitable carriers comprise,but are not limited to, wheat chaff, bran, ground wheat straw,peat-based powders or granules, gypsum-based granules, and clays (e.g.,kaolin, bentonite, montmorillonite). When spores are added to the soil agranular formulation will be preferable. Formulations as liquid, peat,or wettable powder will be suitable for coating of seeds. When used tocoat seeds, the material can be mixed with water, applied to the seedsand allowed to dry. Example of yet other carriers include moistenedbran, dried, sieved and applied to seeds prior coated with an adhesive,e.g., gum arabic. In embodiments that entail formulation of the activesin a single composition, the agronomically acceptable carrier may beaqueous.

The amount of the at least one phosphate solubilizing microorganismvaries depending on the type of seed or soil, the type of crop plants,the amounts of the source of phosphorus and/or micronutrients present inthe soil or added thereto, etc. A suitable amount can be found by simpletrial and error experiments for each particular case. Normally, forPenicillium, for example, the application amount falls into the range of0.001-1.0 Kg fungal spores and mycelium (fresh weight) per hectare, or10²-10⁶ colony forming units (cfu) per seed (when coated seeds areused), or on a granular carrier applying between 1×10⁶ and 1×10¹¹ colonyforming units per hectare. The fungal cells in the form of e.g., sporesand the carrier can be added to a seed row of the soil at the root levelor can be used to coat seeds prior to planting.

In embodiments, for example, that entail use of at least two strains ofa phosphate solubilizing microorganism, such as, two strains ofPenicillium, commercial fertilizers may be added to the soil instead of(or even as well as) natural rock phosphate. The source of phosphorousmay contain a source of phosphorous native to the soil. In otherembodiments, the source of phosphorous may be added to the soil. In oneembodiment the source is rock phosphate. In another embodiment thesource is a manufactured fertilizer. Commercially available manufacturedphosphate fertilizers are of many types. Some common ones are thosecontaining monoammonium phosphate (MAP), triple super phosphate (TSP),diammonium phosphate, ordinary superphosphate and ammoniumpolyphosphate. All of these fertilizers are produced by chemicalprocessing of insoluble natural rock phosphates in large scalefertilizer-manufacturing facilities and the product is expensive. Bymeans of the present invention it is possible to reduce the amount ofthese fertilizers applied to the soil while still maintaining the sameamount of phosphorus uptake from the soil.

In a further embodiment, the source or phosphorus is organic. An organicfertilizer refers to a soil amendment derived from natural sources thatguarantees, at least, the minimum percentages of nitrogen, phosphate,and potash. Examples include plant and animal by-products, rock powders,seaweed, inoculants, and conditioners. Specific representative examplesinclude bone meal, meat meal, animal manure, compost, sewage sludge, orguano.

Other fertilizers, such as nitrogen sources, or other soil amendmentsmay of course also be added to the soil at approximately the same timeas the phosphate solubilizing microorganism or at other times, so longas the other materials are not toxic to the fungus.

Diazotrophs are bacteria and archaea that fix atmospheric nitrogen gasinto a more usable form such as ammonia. Examples of diazotrophs includebacteria from the genera Rhizobium spp. (e.g., R. cellulosilyticum, R.daejeonense, R. etli, R. galegae, R. gallicum, R. giardinii, R.hainanense, R. huautlense, R. indigoferae, R. leguminosarum, R.loessense, R. lupini, R. lusitanum, R. meliloti, R. mongolense, R.miluonense, R. sullae, R. tropici, R. undicola, and/or R. yanglingense),Bradyrhizobium spp. (e.g., B. bete, B. canariense, B. elkanii, B.iriomotense, B. japonicum, B. jicamae, B. liaoningense, B. pachyrhizi,and/or B. yuanmingense), Azorhizobium spp. (e.g., A. caulinodans and/orA. doebereinerae), Sinorhizobium spp. (e.g., S. abri, S. adhaerens, S.americanum, S. aboris, S. fredii, S. indiaense, S. kostiense, S.kummerowiae, S. medicae, S. meliloti, S. mexicanus, S. morelense, S.saheli, S. terangae, and/or S. xinjiangense), Mesorhizobium spp., (M.albiziae, M. amorphae, M. chacoense, M. ciceri, M. huakuii, M. loti, M.mediterraneum, M. pluifarium, M. septentrionale, M. temperatum, and/orM. tianshanense), and combinations thereof. In a particular embodiment,the diazotroph is selected from the group consisting of B. japonicum, R.leguminosarum, R meliloti, S. meliloti, and combinations thereof. Inanother embodiment, the diazotroph is B. japonicum. In anotherembodiment, the diazotroph is R leguminosarum. In another embodiment,the diazotroph is R. meliloti. In another embodiment, the diazotroph isS. meliloti.

Mycorrhizal fungi form symbiotic associations with the roots of avascular plant, and provide, e.g., absorptive capacity for water andmineral nutrients due to the comparatively large surface area ofmycelium. Mycorrhizal fungi include endomycorrhizal fungi (also calledvesicular arbuscular mycorrhizae, VAMs, arbuscular mycorrhizae, or AMs),an ectomycorrhizal fungi, or a combination thereof. In one embodiment,the mycorrhizal fungi is an endomycorrhizae of the phylum Glomeromycotaand genera Glomus and Gigaspora. In still a further embodiment, theendomycorrhizae is a strain of Glomus aggregatum, Glomus brasilianum,Glomus clarum, Glomus deserticola, Glomus etunicatum, Glomusfasciculatum, Glomus intraradices, Glomus monosporum, or Glomus mosseae,Gigaspora margarita, or a combination thereof.

Examples of mycorrhizal fungi include ectomycorrhizae of the phylumBasidiomycota, Ascomycota, and Zygomycota. Other examples include astrain of Laccaria bicolor, Laccaria laccata, Pisolithus tinctorius,Rhizopogon amylopogon, Rhizopogon fulvigleba, Rhizopogon luteolus,Rhizopogon villosuli, Scleroderma cepa, Scleroderma citrinum, or acombination thereof.

The mycorrhizal fungi include ecroid mycorrhizae, arbutoid mycorrhizae,or monotropoid mycorrhizae. Arbuscular and ectomycorrhizae form ericoidmycorrhiza with many plants belonging to the order Ericales, while someEricales form arbutoid and monotropoid mycorrhizae. In one embodiment,the mycorrhiza may be an ericoid mycorrhiza, preferably of the phylumAscomycota, such as Hymenoscyphous ericae or Oidiodendron sp. In anotherembodiment, the mycorrhiza also may be an arbutoid mycorrhiza,preferably of the phylum Basidiomycota. In yet another embodiment, themycorrhiza may be a monotripoid mycorrhiza, preferably of the phylumBasidiomycota. In still yet another embodiment, the mycorrhiza may be anorchid mycorrhiza, preferably of the genus Rhizoctonia.

The methods of the present invention are applicable to leguminous seed,representative examples of which include soybean, alfalfa, peanut, pea,lentil, bean and clover. The methods of the present invention are alsoapplicable to non-leguminous seed, e.g., Poaceae, Cucurbitaceae,Malvaceae, Asteraceae, Chenopodiaceae and Solonaceae. Representativeexamples of non-leguminous seed include field crops such as corn, rice,oat, rye, barley and wheat, cotton and canola, and vegetable crops suchas potatoes, tomatoes, cucumbers, beets, lettuce and cantaloupe.

The invention will now be described in terms of the followingnon-limiting examples. Unless indicated to the contrary, water was usedas the control (indicated as “control”.

EXAMPLES Greenhouse Experiments Example 1 Siratro Seedling Growth InVitro Enhanced by LCO Combinations

Siratro (Macroptilium atropurpureum) seeds were surface-sterilized with10% bleach solution for 10 minutes followed by 3 rinses with sterilizeddistilled water. Seed were then placed in test tubes containing 15 mlsterile solidified agar medium supplemented with the LCOs illustrated inFIGS. 1a and 2a (and which are referred to in the examples as the“soybean LCO” and the “pea LCO”) (with total of 10⁻⁸M concentrationeither alone or in combination). Two other LCOs, i.e., pea LCO or theLCO illustrated in FIG. 5 (which is also referred to in the examples asthe “alfalfa LCO”) was added to soybean LCO to study the effect of theircombinations. Seeds were grown for 7 days under grow light at 20° C.with 16/8 h day/night cycle and then harvested for seedling length.

As reflected by the comparison between soy LCO combined with another LCO(inventive embodiment) and soy LCO alone (non-inventive and comparable),the combination of soy and alfalfa LCO was more effective than soy LCOalone or its combination with pea LCO (FIG. 6). Soybean LCO combinedwith alfalfa LCO produced the tallest seedling when total root and shootlength were summed. This difference was significant.

Example 2 LCO Foliar Application on Cherry Tomato

Based on the findings from the soybean LCO and the alfalfa LCOcombination in Siratro (example 1), further investigation was conductedon tomato. Florida petite cherry tomato plants were grown from seeds ingreenhouse plastic containers and sprayed with soy LCO or itscombination with alfalfa LCO during the initiation of flower buds at 5ml/plant application rate. A second spry was also applied one week afterthe first application. At different maturity, leaf greenness, flowernumber, fruit number and final fruit fresh weight were measured.

The results achieved by the inventive embodiment (soy LCO+alfalfa LCO)showed that there was a slight increase in leaf greenness with LCOcombination as compared to non-inventive and comparable soy LCO (FIGS. 7and 8). In terms of total flower formed over a five-day period, LCOcombination was significantly higher than non-inventive soy LCO.Similarly, when fruit numbers were counted over a six-day period,inventive soy and alfalfa LCO combination turned out to be significantlyhigher than soy LCO (FIGS. 9 and 10). At the end of harvest, the averagefruit number per plant was significantly higher for non-inventive soyLCO and inventive soy-alfalfa LCO combination as compared to controltreatment. However, the average fresh-weight yield of cherry tomatoeswas only significant for soy-alfalfa LCO combination over control andsoy LCO (FIGS. 11 and 12).

Example 3 LCOs and Their Combinations on Tomato Seedling Root Growth

Tomato seeds of var. Royal Mounty were placed in petriplates containingmoist (soaked with treatment solutions) germination paper. Treatmentsolutions were prepared with four different LCOs, namely Pea LCO AC(acylated), Pea LCO NAC (non-acylated), Alfalfa LCO and Soybean LCO. Thetotal LCO concentration used to make a water-based treatment solutionwas maintained at 10⁻⁹ M. Petriplates were then placed in dark at roomtemperature for germination. Eight days after germination, seedlingswere measured with a hand held ruler for their root length.

Results obtained from this experiment indicated that all individual LCOtypes enhanced tomato seedling root length as compared to control butonly certain LCO combinations i.e. pea NAC and soybean LCO, pea AC plussoybean LCO and pea NAC plus alfalfa LCO generated significant rootenhancement as compared to non-inventive and comparable single LCO types(FIG. 8). From the experiment, it appeared to be that for tomatoseedlings, pea NAC and soybean LCO combination was the best of allcombinations. The results also indicate that combinations of certainLCOs was more beneficial for tomato seedlings than others and it may beruled out that combination of all four LCOs was better.

All patent and non-patent publications cited in this specification areindicative of the level of skill of those skilled in the art to whichthis invention pertains. All these publications are herein incorporatedby reference to the same extent as if each individual publication orpatent application were specifically and individually indicated to beincorporated by reference.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

The invention claimed is:
 1. A method of enhancing plant growth,comprising treating a plant seed with an effective amount of at leasttwo distinct lipo-chitooligosaccharides (LCOs), said at least twodistinct LCOs comprising the following two LCOs:

wherein said at least two distinct LCOs synergistically enhance growthof a plant that germinates from said seed.
 2. The method of claim 1,wherein at least one of the at least two distinct LCOs is obtained froma strain of rhizobia.
 3. The method of claim 2, wherein the strain ofrhizobia is selected from the group consisting of Rhizobium sp., andBradyrhizobium sp.
 4. The method of claim 1, wherein at least one of theat least two distinct LCOs is obtained from B. japonicum.
 5. The methodof claim 1, wherein at least one of the at least two distinct LCOs isobtained from R. leguminosarum biovar viciae.
 6. The method of claim 1,wherein the at least two distinct LCOs comprise a recombinant LCO. 7.The method of claim 6, wherein the recombinant LCO has a purity of atleast 60%.
 8. The method of claim 6, wherein the recombinant LCO has apurity of at least 70%.
 9. The method of claim 6, wherein therecombinant LCO has a purity of at least 80%.
 10. The method of claim 6,wherein the recombinant LCO has a purity of at least 90%.
 11. The methodof claim 1, wherein the at least two distinct LCOs comprise a syntheticLCO.
 12. The method of claim 1, wherein the at least two distinct LCOsare applied to the seed prior to planting and/or at about the time ofplanting.
 13. The method of claim 12, wherein the effective amount ofthe at least two distinct LCOs is from about 10⁻⁵ to about 10″¹⁴ Molar.14. The method of claim 1, wherein the at least two distinct LCOs areapplied to the seed in furrow.
 15. The method of claim 14, wherein theeffective amount of the at least two distinct LCOs is from 1 μg/acre toabout 70 μg/acre.
 16. The method of claim 1, wherein the at least twodistinct LCOs are applied to the seed at least one month prior toplanting.
 17. The method of claim 1, wherein the at least two distinctLCOs are applied to the seed at least 1 year prior to planting.
 18. Themethod of claim 1, further comprising applying at least oneagronomically beneficial agent to the seed and/or to the plant thatgerminates from the seed.
 19. The method of claim 1, further comprisingapplying at least one micronutrient to the seed and/or to the plant thatgerminates from the seed.
 20. The method of claim 19, wherein the atleast one micronutrient is selected from the group consisting ofvitamins and trace minerals.
 21. The method of claim 1, furthercomprising applying at least one plant signal molecule to the seedand/or to the plant that germinates from the seed.
 22. The method ofclaim 1, wherein the plant signal molecule is a chitooligosaccharide(CO) to the seed and/or to the plant that germinates from the seed. 23.The method of claim 21, wherein the plant signal molecule is selectedfrom the group consisting of chitinous compounds, flavonoids, jasmonicacid and derivatives thereof, linoleic acid and derivatives thereof,linolenic acid and derivatives thereof, and karrikins and derivativesthereof.
 24. The method of claim 1, further comprising applying one ormore herbicides, insecticides, and/or fungicides to the seed and/or tothe plant that germinates from the seed.
 25. The method of claim 1,further comprising applying one or more phosphate solubilisingmicroorganisms, diazotrophs (Rhizobial inoculants), and/or mycorrhizalfungi to the seed and/or to the plant that germinates from the seed. 26.The method of claim 1, further comprising applying one or more phosphatesolubilizing strains of the fungus Penicillium to the seed and/or to theplant that germinates from the seed.
 27. The method of claim 1, furthercomprising applying one or more phosphate solubilizing strains of P.bilaiae to the seed and/or to the plant that germinates from the seed.28. The method of claim 27, wherein the strain of P. bilaiae is selectedfrom the group consisting of NRRL 50162, NRRL 50169, ATCC 20851, ATCC22348, and ATCC
 18309. 29. The method of claim 1, further comprisingapplying one or more phosphate solubilizing strains of P. gaestrivorusto the seed and/or to the plant that germinates from the seed.
 30. Themethod of claim 1, wherein the seed is leguminous.
 31. The method ofclaim 30, wherein the leguminous seed is soybean.
 32. The method ofclaim 1, wherein the seed is non-leguminous.
 33. The method of claim 32,wherein the non-leguminous seed is a field crop seed.
 34. The method ofclaim 33, wherein the field crop seed is corn.
 35. The method of claim32, wherein the non-leguminous seed is a vegetable crop seed.
 36. Themethod of claim 1, wherein the seed is tomato.
 37. The method of claim1, further comprising applying one or more strains of Bradyrhizobium tothe seed and/or to the plant that germinates from the seed.
 38. Themethod of claim 1, further comprising applying one or more strains ofRhizobium to the seed and/or to the plant that germinates from the seed.39. The method of claim 1, further comprising applying one or morestrains of Sinorhizobium to the seed and/or to the plant that germinatesfrom the seed.
 40. The method of claim 1, further comprising applyingone or more strains of mycorrhizal fungi to the seed and/or to the plantthat germinates from the seed.